In the experiments on the anesthetized dogs, the effects of ATP-sensitive potassium (KATP) channels activation by flocalin on the activity of endothelial and inducible NO-synthases (iNOS), heme oxygenase reaction, blood oxygenation and free radical processes were studied. Changes in biochemical parameters in arterial blood were determined after 20 and 60 minutes after intravenous administration of flocalin in doses of 0.1, 0.5, 1.0 and 1.5 mg/kg. It is shown that the opening of KATP-channels dose-dependent increases the level of protective constitutive synthesis of nitric oxide and, conversely, inhibits inducible synthesis (at 2.8 and 2.1 times at a dose of flocalin 1.5 mg/kg, respectively). The activation of the above channels is a powerful antihypoxic mechanism – greatly enhances the oxygenation of arterial blood and the content of nitrite anion (at 3.7 and 3.0 times at a dose of 1,0 mg/kg, respectively). Flocalin significantly reduced the content of the products of the heme oxygenase reaction - iron and bilirubin (with a maximum effect of 2.9 and 1.9 times respectively), which may indicate inhibition of the activity of the enzyme heme oxygenase. Аctivation of KATP-channels dose-dependently suppresses free radical processes (decrease in the generation of superoxide anion and hydrogen peroxide (5.3 and 7.2 times at a dose of 1.5 mg/kg, respectively) and exhibits antioxidant properties (decrease in the content of diene conjugates by 6.3 times at a dose of 1.5 mg/kg), inhibits the formation of peroxynitrite by reducing the generation of superoxide anion (uric acid content) and inducible nitric oxide. Thus, the activation of KATP-channels by flocalin increases the constitutive synthesis of NO and, conversely, reduces the inducible synthesis of NO, greatly enhances the oxygenation of arterial blood, suppresses free radical processes and the activity of heme oxygenase.